Câu a:

x/3 + 1/5 = 3/4

=> x/3 = 3/4 - 1/5

=> x/3 = 11/20.

=> x= 11/7

a)\(\frac{x}{3}+\frac{1}{5}=\frac{3}{4}\)

\(\frac{x}{3}=\frac{3}{4}-\frac{1}{5}\)

\(\frac{x}{3}=\frac{15}{20}-\frac{4}{20}\)

\(\frac{x}{3}=\frac{11}{20}\)

\(x:3=\frac{11}{20}\)

\(x=\frac{11}{20}.3\)

\(x=\frac{11}{20}\cdot\frac{3}{1}\)

\(x=\frac{33}{20}\)

\(x=1,65\)

\(P=\left(1+\frac{\sqrt{a}-1}{a-\sqrt{a}}\right):\left(\frac{a+\sqrt{a}}{a-1}+\frac{\sqrt{a}}{a-\sqrt{a}}\right)\left(a>0;a\ne1\right)\)

\(P=\frac{a-\sqrt{a}+\sqrt{a}-1}{\sqrt{a}\left(\sqrt{a}-1\right)}:\left[\frac{\sqrt{a}\left(\sqrt{a}+1\right)}{\left(\sqrt{a}-1\right)\left(\sqrt{a}+1\right)}+\frac{\sqrt{a}}{\sqrt{a}\left(\sqrt{a}-1\right)}\right]\)

\(P=\frac{a-1}{\sqrt{a}\left(\sqrt{a}-1\right)}:\left(\frac{\sqrt{a}}{\sqrt{a}-1}+\frac{1}{\sqrt{a}-1}\right)\)

\(P=\frac{\left(\sqrt{a}-1\right)\left(\sqrt{a}+1\right)}{\sqrt{a}\left(\sqrt{a}-1\right)}:\left(\frac{\sqrt{a}+1}{\sqrt{a}-1}\right)\)

\(P=\frac{\sqrt{a}+1}{\sqrt{a}}:\frac{\sqrt{a}+1}{\sqrt{a}-1}\)

\(P=\frac{\sqrt{a}+1}{\sqrt{a}}.\frac{\sqrt{a}-1}{\sqrt{a}+1}=\frac{\sqrt{a}-1}{\sqrt{a}}\)

Vậy .............

_Minh ngụy_

\(P=\left(1+\frac{\sqrt{a}-1}{a-\sqrt{a}}\right):\left(\frac{a+\sqrt{a}}{a-1}+\frac{\sqrt{a}}{a-\sqrt{a}}\right)\text{ (ĐKXĐ: }x\ne1;x\ne0\text{ )}\)

\(P=\left(\frac{a-\sqrt{a}}{a-\sqrt{a}}+\frac{\sqrt{a}-1}{a-\sqrt{a}}\right):\left(\frac{\left(a+\sqrt{a}\right)\left(a-\sqrt{a}\right)}{\left(a-1\right)\left(a-\sqrt{a}\right)}+\frac{\sqrt{a}\left(a-1\right)}{\left(a-\sqrt{a}\right)\left(a-1\right)}\right)\)

\(P=\frac{a-\sqrt{a}+\sqrt{a}-1}{a-\sqrt{a}}:\left(\frac{a^2-a}{\left(a-1\right)\left(a-\sqrt{a}\right)}+\frac{\sqrt{a}\left(a-1\right)}{\left(a-\sqrt{a}\right)\left(a-1\right)}\right)\)

\(P=\frac{a-1}{a-\sqrt{a}}:\frac{a\left(a-1\right)+\sqrt{a}\left(a-1\right)}{\left(a-1\right)\left(a-\sqrt{a}\right)}\)

\(P=\frac{a-1}{a-\sqrt{a}}:\frac{\left(a-1\right)\left(a+\sqrt{a}\right)}{\left(a-1\right)\left(a-\sqrt{a}\right)}\)

\(P=\frac{a-1}{a-\sqrt{a}}:\frac{a+\sqrt{a}}{a-\sqrt{a}}\)

\(P=\frac{a-1}{a-\sqrt{a}}\times\frac{a-\sqrt{a}}{a+\sqrt{a}}\)

\(P=\frac{a-1}{a+\sqrt{a}}\)

\(\frac{2-x}{4}=\frac{3x-1}{-3}\)

\(3\left(2-x\right)=-4\left(3x-1\right)\)

\(6-3x=-12x+4\)

\(6-3x+12x=4\)

\(6-9x=4\)

\(9x=4-6\)

\(9x=-2\)

\(x=-\frac{2}{9}\)

\(1,2\div0,8=\left(-3,6\right)\div\left(3x\right)\)

\(1,5=\left(-3,6\right)\div3x\)

\(3x=\left(-3,6\right):1,5\)

\(3x=-2,4\)

\(x=-0,8\)

\(1,2\div8=\left(-3,6\right)\div3x\)

\(\Leftrightarrow\frac{3}{20}=\frac{-12}{x}\)

\(\Rightarrow3x=-240\)

\(\Rightarrow x=-80\)

~Std well~

#Tử_Trân

\(\frac{1}{y\left(x-y\right)}-\frac{1}{x\left(x-y\right)}=\frac{x-y}{y\left(x-2\right)x}=\frac{1}{yx}\)

-tham khảo tại bài mà mình đã giải tại đây-

Câu hỏi của Trần Nam Hải - Toán lớp 9 - Học toán với OnlineMath

https://olm.vn/hoi-dap/detail/228029923283.html

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_Minh ngụy_

\(A=\frac{1}{1-\sqrt{a}}+\frac{a\sqrt{a}}{\sqrt{a}-1}\left(\text{ĐKXĐ: a}\ne1\right)\)

\(A=\frac{-1}{-\left(1-\sqrt{a}\right)}+\frac{\left(\sqrt{a}\right)^2.\sqrt{a}}{\sqrt{a}-1}\)

\(A=\frac{-1}{\sqrt{a}-1}+\frac{\sqrt{a}^3}{\sqrt{a}-1}\)

\(A=\frac{-1+\sqrt{a}^3}{\sqrt{a}-1}\)

\(A=\frac{\sqrt{a}^3-1}{\sqrt{a}-1}\)

\(A=\frac{\left(\sqrt{a}-1\right)\left(a+\sqrt{a}+1\right)}{\sqrt{a}-1}\)

\(A=a+\sqrt{a}+1\)